Red-Yellow Argisol Research Articles

Influence of Vinasse and Mechanized Harvesting on the Physical and Chemical Aspects of Soil in Paudalho Municipality - PE

Sugarcane cultivation methods and processes usually have negative impacts on the environment. However, this industry has been seeking more sustainable technologies, ranging from the adequate disposal of the organic residues produced to the elimination of pre-harvest burning and introduction of mechanized harvest. The objective of this work was to verify the influence of vinasse application and mechanized harvesting on the physical and chemical aspects of a dystrophic Red Yellow Argisol of medium texture, cultivated with sugarcane. For this, a field experiment in a Completely Randomized Design, with a factorial scheme was conducted. Four management treatments, with three replications, were evaluated: T1 - Without application of vinasse, burned cane followed by manual harvest, without irrigation; T2 - With application of vinasse, mechanized harvest, without irrigation; T3 - With application of vinasse, mechanized harvest, with irrigation; T4 - With application of vinasse, burned cane followed by manual harvest, without irrigation. Soil samples were collected in three depths (0 – 20 cm, 20 – 40 cm and 40 – 60 cm) and soil physical and chemical characteristics were determined. The data obtained were submitted to ANOVA and compared by the Tukey test (p≤0.05) of probability, using the statistical program ASSISTAT 7.7 beta. The results showed that fertigation with vinasse did not influence soil density, particle density, and total porosity. However, mechanized harvesting increased soil density and total porosity. The soil in the experimental unit without vinasse application presented a more acidic pH and high levels of aluminum saturation, causing a decrease in the availability of nutrients, and the soils treated with vinasse had an increase in nutrient availability. Therefore, the addition of vinasse can be an important strategy in maintaining and increasing long-term soil fertility in sugarcane cropping systems.

Influência do nitrogênio na produtividade do pimentão em condições de campo aberto no outono-inverno

ABSTRACT Nitrogen (N) deserves special attention in the fertilization recommendation for bell peppers, as it is the nutrient absorbed in greater quantity, standing out for the amount required and the functions it performs in the plant. The objective was to evaluate the influence of nitrogen applied as top dressing on bell pepper production in open field during the autumn/winter period. The experiment was conducted in Red-Yellow Argisol. A randomized complete block design with four replications was used. Treatments consisted of nitrogen rates applied as top dressing (0, 75; 150; 300; and 450 kg/ha). Nitrogen increased the number and fresh mass of fruits per plant. The SPAD Reading increased with the increment of nitrogen rates in the three evaluation periods and with the evaluation period. Bell peppers grown during the autumn/winter period showed high productive potential associated with nitrogen rates higher than currently recommended. The yield of marketable fruits increases until 214 kg/ha of N. The critical level for the SPAD reading varied with the age of the plants, with estimated critical values of 53.2, 66.5, and 61.9 at 35, 56, and 154 days after transplanting (DAT).

Partição de fotoassimilados em plantas de quiabo submetidas a doses de nitrogênio

ABSTRACT Nitrogen (N) is the third nutrient more absorbed by okra. Therefore, an adequate supply of this element is essential for okra growth through the accumulation of dry matter in the leaves, stem, root and fruit. The objective was to evaluate the influence of N doses on growth, photoassimilates partition and yield of okra. The experiment was carried out in a Red-Yellow Argisol. A randomized complete block design with four replicates was used. The treatments consisted of N doses applied as topdressing (0, 60, 120, 240, 360 kg/ha). Samples of plants were held at 60, 75, 90, 105, 120, 135, 150 and 165 DAS for determination of the plant’s dry weight. The plant showed slow growth until 70 days, and after that time, intensified its growth until the end of the cycle. Total dry mass and absolute plant growth rate increased with increasing N availability, reaching the maximum marketable fruit yield of 10,665 kg/ha with 346 kg/ha N. The growth and partition of photoassimilates among the organs of the okra plant ‘Santa Cruz’ are altered with increasing nitrogen availability applied in topdressing.

Atributos químicos do solo sob combinações de adubação orgânica e salinidade da água

ABSTRACT The use of brackish water causes chemical changes in cultivated soils. It is therefore necessary to apply strategies that can minimize its negative impacts, such as the use of organic fertilizers. This study aimed to evaluate in the field the chemical attributes of a Red Yellow Argisol under irrigation with saline water and organic fertilizing in an area cultivated with corn. The design was randomized blocks, in a split-plot scheme, with the plots comprising salinity levels for the irrigation water (0.8 and 3.0 dS m-1) and the subplots combinations of organic fertilizers (cattle manure + poultry biofertilizer + goat biofertilizer; cattle manure + goat biofertilizer; cattle manure + poultry biofertilizer; control), with four replications. The 3.0 dS m-1 irrigation has a negative effect on the soil chemical attributes, particularly reducing the pH and increasing the sodium, exchangeable sodium percentage and electrical conductivity of the soil saturation extract. The combination of cattle manure + poultry biofertilizer + goat biofertilizer mitigates the salt stress by favouring the accumulation of nitrogen and organic matter, while the cattle manure + poultry biofertilizer favours the potassium accumulation in the soil. The combination of cattle manure + poultry biofertilizer + goat biofertilizer increases the contents of phosphorus and potassium when using the 0.8 dS m-1 irrigation.

Kinetics and mineralization fraction of organic matter from sewage sludge mixed with soil under controlled laboratory conditions

The objective of this work was to evaluate the kinetics and mineralization fraction of organic matter from sewage sludge mixed with the soil under controlled laboratory conditions. For this, organic material samples accumulated in layers 0–5 cm, 5–10 cm and 10–15 cm in relation to the surface of a vertical flow constructed wetland system (VF-CW) used for treatment of septic tank sludge, in addition to samples of dewatered sludge from a septic tank and a UASB reactor and non-dewatered sludge from an anaerobic digester were mixed with material collected from the surface layer of a Red Yellow Argisol at rates equivalent to the applications, via organic residues, of 300 and 600 kg ha−1 year−1 of total nitrogen. It was found that the two-phase kinetic equation fit better to the mineralization data of labile and recalcitrant organic carbon. For the lowest nitrogen application rate in the mixtures, the mineralization fractions of the total organic carbon were higher than 73%, while at the highest dose there was a reduction in the mineralization of organic matter by 17% and 63%, respectively in samples collected in layer 10–15 cm from the VF-CW and in the septic tank sludge dewatered in the drying bed.

Leaching of N and Initial Development of Maize as a Function of Urea and Urea Doses Coated with Sulfur

Urea is the most important source among nitrogen fertilizers, but leaching losses are highly susceptible. The fertilizer industry has the challenge of improving the chemical characteristics of fertilizers, ensuring the best efficiency in the application and utilization of nutrients. An alternative is sulfur treatment to reduce this problem. The present work had as objective to evaluate the soil nitrogen loss by leaching, treated with urea doses with and without sulfur coating (FH Nitro Gold®). For this, leaching experiments were set up in the laboratory and initial corn cultivation in a greenhouse. The soil used was classified as Red Yellow Argisol, collected at the UFS Rural Campus. Two treatments were applied, which consisted of the application of the two sources of Nitrogen, with doses of 0, 50, 100, 150, 200 and 250 kg per hectare, where nitrogen losses were evaluated by leaching (ammonium, nitrate and total N). A second leaching experiment was set up at the following rates: 0, 25, 50, 75, 100 and 125 kg per hectare, and after leaching the corn was cultivated for 30 days under greenhouse conditions. After 30 days of cultivation, the biometric parameters were assessed (leaf number, stem diameter and height of plants). The source of nitrogen fertilizer coated with sulfur provided reduction of nitrogen loss by leaching when compared to uncoated urea. The application of coated urea presents higher soil nitrogen absorption and better results in the development of maize plants grown under greenhouse conditions.

Physical and hydrological characteristics and modelling of the soil water retention curve in the brazilian semi-arid region

Semiarid regions are characterised by water scarcity, a limiting factor on plant growth and development. The Sertão Canal was built in the semiarid region of Brazil, more specifically in the state of Alagoas, with the aim of making year-round irrigation possible. However, for the best water management, a physical and hydrological knowledge of the soils is necessary. As such, the aim of this study was to determine the physical and hydrological characteristics of three different types of soil (Argisol, Quartzarenic Neossol and Regolithic Neossol) under native vegetation (Caatinga) and agricultural systems in the semiarid region of Alagoas, as well as to adjust the soil water retention characteristic curves. Soil samples were collected at depths of 0-10, 10-20 and 20-30 cm in the municipalities of Inhapi, Delmiro Gouveia and Pariconha, in the state of Alagoas. The points of the moisture characteristic curve were determined by the Richards method, at pressures of 33, 100, 500, 1000 and 1500 kPa. Retention curves were modelled using the exponential decay equation and compared using the van Genuchten equation, modelled with the help of the RETC computer software. Particle size varied according to the textural classification of the different soils, from Sand to a Sandy Clay Loam. The retention curve fluctuated due to the particle size of the soil, with the Red-Yellow Argisol (Inhapi) having a greater capacity for water retention. Extremely sandy soils, such as those in the Delmiro Gouveia region, had a low capacity for retaining water. For each soil sample, the exponential decay equation gave the best fit, with values for R2adjust of greater than 0.93. When the measured soil moisture levels were compared with the levels estimated by the RETC model, some of the treatments were unable to estimate accurately the moisture levels obtained with the soil water retention curves.

Gas exchanges in the zucchini culture fertilized with biofertilizers in two types of soil

The application of biofertilizers may provide plants similar performance and even superior to the use of mineral fertilizers, therefore, the determination of the most suitable sources to be applied in different crops is relevant. Given the importance of gas exchange in the performance of crops and that biofertilizers can provide increases in these physiological parameters, this study aimed to evaluate gas exchange in zucchini plants cultivated in two types of soil and managed with different aerobic fermentation biofertilizers. The experiment was carried out in full sunlight, in pots, using a randomized blocks design in an arrangement of split plots. The plots consisted of two types of soil (S1: Red-Yellow Argisol and S2: Fluvic Neossol), subdivided plots into five aerobic fermentation biofertilizers (F1 = quail, F2 = sheep, F3 = mixed - bovine + quail + sheep, F4 = bovine, and F5 = enriched crab), with five replicates. At 45 days after transplanting, the following variables were analyzed: photosynthesis, stomatal conductance, transpiration, internal CO2 concentration, leaf temperature, and chlorophyll. Bovine, sheep, and mixed biofertilizers showed the highest rates with the best performance of Italian zucchini cultivation. The types of soil studied concerning the rates did not have a significant effect between treatments on zucchini cultivation. Moreover, Chlorophyll was not significantly influenced by any of the treatments applied.

Mineralization of Nitrogen Forms in Soil Cultivated with Yellow Melon under Organic and Mineral Fertilization

ABSTRACT The association of mineral and organic fertilization is a nitrogen supply system for the melon crop. Nitrogen (N) fractionation is an important tool to understand its dynamics in the soil and the contribution of each fraction to N bioavailability. This study aimed to evaluate the effects of organic and mineral fertilization on organic and inorganic forms of soil N of the cultivation of yellow melon. The experiment was conducted in the Experimental Field of Pacajus, belonging to Embrapa Agroindústria Tropical, in soil classified as Red Yellow Argisol. The experimental design was a split-plot randomized block. Fertilizer application was the main plot treatment and sampling time was arranged as subplots. The experimental results indicated that only organic fertilization was sufficient to significantly increase the total-N content (varying from 1,127 mg kg−1 to 967 mg kg−1) compared to only mineral fertilization (951 mg kg−1) and organic N represented 92 ± 2% of the total-N. In addition, the higher hydrolyzable N content was observed in the treatment with only bovine manure application (542 mg kg−1) which represents an N source for the mineralization and subsequent inorganic N for plants. Our results reveal that organic fertilization is efficient for long-term fertility management, increasing melon productivity.

Arduino system and ultrasonic sensor for automation of the determination of water infiltration rate in soil

The velocity of water infiltration in soil is important for the design of irrigation systems, drainage, septic tanks, sanitary landfills, dams, channels for water distribution, soil and water management to control erosion and estimate surface runoff. Infiltration tests are generally done with rulers and visual reading, which can lead to errors. The present study therefore aimed to determine the Infiltration Velocity (IV) curves of water in the soil by the concentric ring infiltrometer method, using an Arduino microcontroller and an ultrasonic sensor to measure the lowering of the water depth. For that, in the same infiltration test, four readings in Automatic mode (AT) and four readings in Manual mode (MN) were performed simultaneously, in a red-yellow Argisol type soil, in the Areal Basin, located in the southeastern region of Brazil. municipality of Taubaté, Vale do Paraíba, in the state of São Paulo. Adjustments of kostiakov curves and their equations were made from the data obtained in the field, and the values of R² were determined, as well as the values of Basic Infiltration Velocities (BIV), Accumulated Infiltration (AI) and the Average Percentage Error (APE) of the calculated IS values and those estimated by the equations. The results show that the number of readings in the same test time in Automatic mode (AT) was 2.3 times higher than in the manual (MN). All tests showed that the Red-Yellow Argisol showed a high infiltration speed, and in the pasture area the BIV values were 1.9 times higher than those obtained in the forest area. The R² determination coefficients for all curves are 0.99 in all tests and demonstrate the strong correlation between the data. The APE of the calculated and estimated IS values were low, and the biggest discrepancies that occurred were (APE = 0.30%) in the MN - 4 test and (APE = -0.01%) in the AT - 4. APE of MN mode BIVs for AT was 2.7%. These differences in IS values are reflected in the accumulated infiltration (AI) in the soil over time, and in this study the AI of the ATs tests was on average 4.1mm higher than in the MN tests, which corresponds to a difference of 41m³ ha-1. It was concluded that the use of the Arduino microcontroller with the ultrasonic sensor installed in the ring infiltrometer proved to be efficient in the field measurements and made the determination of the accumulated infiltration and the infiltration speed practical, proving to be an economical and technically viable alternative mainly due to the quantity of possible points to collect for each test and the greater reliability added to the low error values when compared to the manual.

GROWTH, YIELD AND POST-HARVEST EVALUATION OF LETTUCE PLANTS SUBJECTED TO DIFFERENT LEAF SILICON CONCENTRATIONS

Lettuce is considered the most produced and consumed leafy vegetable; however, it has short post-harvest life, which generates significant losses for both producers and consumers. Studies have proven the beneficial effect of silicon on fruits and vegetables. Therefore, the aim of the current study is to evaluate the influence of leaf calcium silicate application on the growth, biomass production and postharvest conservation of curly lettuce. The experiment was carried out in greenhouse at Federal Rural University of Amazonia, Parauapebas Campus / PA. It followed a completely randomized design (CRD) with five Si concentrations (0.0, 2.0, 4.0, 6.0 and 8.0 mg L-1) and eight repetitions, which totaled 40 plants. Plants were grown in plastic pots (capacity = 3 dm3) filled with soil classified as Red-Yellow Argisol. Different Si concentrations were applied to plant leaves, at the 20th and 27th days after transplantation (DAT). Silicon has favored the growth and development of lettuce plants, as well as reduced their post-harvest weight loss. It was possible concluding that the herein tested Si concentrations, which were applied to leaves - in the form of calcium silicate - had beneficial effect on lettuce plants.

Establishing <i>Cratylia argentea</i> in an Ultisol in the West of Acre, Southwestern Amazon, Brazil

Cratylia argentea is a multi-purpose shrub with potential as a source of protein for livestock, but is rarely used in production units. This study aimed to monitor the establishment of a stand of this plant in a sandy Ultisol (Red-Yellow Argisol), in an area of 4,000 m2 on a rural property in Cruzeiro do Sul, Acre, Brazil, comparing 2 planting methods: (i) transplanting seedlings (78 in total); and (ii) direct seeding (3,820 seeds in 1,910 pits). The existing pasture was sprayed with glyphosate before planting C. argentea. Subsequently, herbicide and mechanical methods were used to control weeds, while fertilizer was applied and the area was mulched. In the first year after planting, activities performed and inputs were recorded along with costs in order to create a reference model for those intending to cultivate this species in the humid tropics. At 10 months after planting, average height of plants was 162 cm (range 70‒240 cm) with no effect of planting method. Ninety-seven per cent of plants established from seedlings survived, while 81% of pits established from direct seeding in the field had surviving plants. The cost of establishing a hectare of C. argentea was US$ 1,654.17, with 85.8% of the cost for labor and only 14.2% for other inputs, although costs of producing seedlings and hand-planting them were not considered. Studies to develop planting systems using less labor seem warranted.

Nitrogen fertilization in Brachiaria decumbens Stapf grass under degraded soil condition

Chemically degraded soils are found all over the world. Fertilization is an essential agronomic technique for recovering fertility and productivity in these areas. In this context, the objective was to recover the productive capacity of a degraded Red Yellow Argisol, grown with Brachiaria decumbens Stapf, in the presence of mineral fertilization with increasing amounts of nitrogen, evaluating the production of plant mass, plant height, tillering and water consumption. The experiment was conducted in a screened shelter and humidity control, according to a completely randomized experimental design. The treatments were organized in a factorial scheme, 6 treatments (without fertilization, 0, 30, 60, 90, 120 of nitrogen; 80 and 50, phosphorus and potassium for all treatments in g vase-1, respectively) corresponding to the amount of fertilizer applied in Kg ha-1, 4 cuts (performed every 30 days, starting 45 days after planting) and 5 repetitions. When fertilizing with 120 Kg ha-1 of nitrogen, it was obtained increase in fresh (655%) and dry (685%) mass when compared to the phytomasses of the treatment without fertilization, there was also an increase in the number of effective tillers and plant height, as the amounts of nitrogen applied increased in the soil. The maximum amount of nitrogen to be applied to the soil, in order to produce phytomass of B. decumbens in the condition of chemical degradation of the soil, obtained in the work was 120 Kg ha-1. In addition, the work allowed us to conclude that fertilization is an inexpensive and very important technique to recover the productive capacity of forage in the micro region of Brejo Paraibano, Northeast Brazil.

Potassium Fertilization in Sugarcane Ratoon Yield Grown in a Tropical Region

ABSTRACTPotassium (K) is closely associated to the improvement of sugarcane quality, acting in the conversion of reducing sugar (RS) to recoverable sugars (TRS). The present study aimed to evaluate the effect of different levels of K-fertilization on the yield and technological quality of sugarcane ratoons grown under edaphoclimatic conditions in the Brazilian central region. The experiment was carried out using the sugarcane variety CTC-4, in a Distrofic Latosols, medium texture (270 g clay kg−1). The study was arranged in a randomized complete block design, with five treatments (0; 50; 100; 150 and 200 kg K2O ha−1), and five replicates. Potassium content in soil and plant, biometric variables, stalk yield and the technological quality at harvest were evaluated. The 200 kg ha−1 dose increased the K content in 160, 156, 56 and 3% in 0–0.20 and 0.20–0.40 m layers at 180 and 360 days after budding (DAB), respectively, promoting greater absorption of the nutrient by plants (X ̅ = 15.22 g kg−1). The higher potassium absorption reflected in yield gains, with an increasing of 7.9%, compared to the control treatment, yielding 100.37 t ha−1. However, soil K fertilization did not affect the technological quality of the sugarcane ratoon.Abbreviations: K: potassium; RS: reducing sugars; TRS: recoverable sugars; DAB: days after budding; SB: Sum of Bases; CEC: Cation Exchange Capacity; V: Saturation Base; Kcl: potassium chloride; AWC: Available water capacity; PC: Pol percent in sugarcane; Brix: total soluble solids; dRYL: Dystrophic Red Yellow Latosol; eRYA: Eutrophic Red Yellow Argisol.

Estudo da sorção de chumbo em solos intemperizados e em suas diferentes frações

Dentre os processos de acúmulo de metais tóxicos pelo solo, como o chumbo (Pb), o de adsorção é um dos mais notados. No solo, a adsorção refere-se à passagem de um soluto da fase aquosa para a superfície de um adsorvente sólido. Considerando-se que as isotermas de adsorção no solo muitas vezes variam fortemente de solo para solo, são necessários estudos mais detalhados do comportamento de metais em solo brasileiro, para melhor adequação dos modelos às condições climáticas e ambientais brasileiras. Assim, o objetivo é estudar a adsorção de chumbo (Pb) em um Latossolo Vermelho Amarelo (LVA) e um Argissolo Vermelho Amarelo (AVA) e em suas diferentes frações granulométricas. Para determinar a relação entre a quantidade de um composto adsorvido a partir de soluções pelo solos, a várias concentrações, e a quantidade remanescente nessas soluções, são utilizadas isotermas de adsorção que geram resultados quantitativos. Foi também calculado o coeficiente de distribuição (Kd) do metal pelos solos e pelas suas diferentes frações. Neste estudo, em específico, foi possível verificar que a maior adsorção de Pb+2 foi observada pela fração silte + argila dos solos, segundo as isotermas. Quanto à classificação das isotermas, o AVA apresentou isotermas do tipo L e o LVA do tipo H. A partir dos valores de Kd percebe-se que o chumbo apresenta uma alta afinidade pelo LVA e baixa afinidade pelo AVA. Concluindo, que o modelo de Freundlich adequou-se bem aos resultados experimentais de adsorção de chumbo pelos solos.

Ecotoxicity test as an aid in the determination of copper guideline values in soils

ABSTRACT: The process of identifying a contaminated area involves a preliminary assessment consisting of chemical analysis and comparison with guideline values. In Brazil, these values are included in the CONAMA Resolution no. 420/2009, based on chemical analysis and phytotoxicity. The objective of this research was to evaluate the ecotoxicity of copper in two natural soils in the state of Rio de Janeiro, a Haplic Planosol (sandy) and a Red-Yellow Argisol (medium texture), to verify if the values established by the legislation offer protection to the soil fauna. Lethality and reproduction tests were performed with Eisenia andrei worms and Folsomia candida springtails. Results indicated copper values in Planosol as LC50 435 mg kg 1 and EC50 29 mg kg 1 for E. Andrei and LC10 137 mg kg 1 and EC50 117 mg kg 1 for F. candida. In Argisol, these results were LC50 690 mg kg 1 and EC50 61 mg kg 1 for E. andrei, and LC10 42 mg kg 1 and EC50 138 mg kg 1 for F. candida. Values reported are lower than the research value (200 mg kg-1) established by the CONAMA resolution 420/09, indicating that concentrations lower than the limit values may affect these organisms, depending on the type of soil. Worms were more sensitive than springtails to copper contamination, and sandy soil was more susceptible to ecotoxicity due to copper contamination, probably due to the greater bioavailability of the metal. Results of such ecotoxicity tests should be considered in the development of soil guideline values.

Selection of arbuscular mycorrhizal fungi for sugarcane in four soils with the presence of dark septate endophytes

The present study aimed to select efficient arbuscular mycorrhizal fungi (AMF) for sugarcane growth and P nutrition in four soils that spontaneously contained dark septate endophytes (DSE). The effect of nine AMF isolates was evaluated individually in sugarcane presprouted seedlings (SP81-3250) grown under greenhouse conditions for a 120-day period. The isolates that stimulated plant growth in the soils with low P availability were Acaulospora colombiana (ACOL), Claroideoglomus etunicatum (CETU), Gigaspora margarita (GMAR), Rhizophagus clarus (RCLA) and Scutellospora calospora (SCAL). Compared to the Yellow Argisol, which had the highest P level, the Red-Yellow Argisol, with an intermediate P content, increased plant height. Compared to the other treatments, inoculation with ACOL, RCLA, and SCAL resulted in higher foliar P content in plants grown in soils with high to intermediate P levels. Root colonization by AMF and DSE was verified in the plants, with the coexistence of both fungal groups in the same plant and/or root fragment. However, AMF colonization was low compared to DSE colonization. The cooccurrence of DSE and AMF was higher in the plants inoculated with ACOL, RCLA, SCAL, and Dentiscutata heterogama. ACOL, CETU, GMAR, RCLA, and SCAL are AMF isolates that have the potential to establish a mycorrhizal inoculant for sugarcane that would be effective in several soils.

Yield responses of Macrotyloma axillare (family Fabaceae) to combinations of doses of phosphorus and calcium

The present study aimed to assess the effects of combinations of doses of phosphorus and calcium on the yield characteristics of Macrotyloma axillare access NO 279 (family Fabaceae) in a Red-Yellow Argisol with average P level (24 mg dm-3). The experiment was carried out in greenhouse in Nova Odessa/SP, Brazil, from August to December 2015. A 52 fractional factorial design with 13 combinations for doses of phosphorus and calcium in mg dm-3: 0-0; 0-40; 0-80; 15-20; 15-60; 30-0; 30-40; 30-80; 45-20; 45-60; 60-0; 60-40; 60-80, in a randomized complete block design with four replications. Two cuttings were made on the plants. The phosphorus x calcium interaction and the isolated doses of calcium were not significant for the parameters assessed. The production of dry biomass of the aerial part, the leaf area, the number of leaves and the number of branches of Macrotyloma showed significant responses to the isolated doses of phosphorus applied in the primary growth. In the secondary growth, only the number of branches and the dry biomass production of the dead material responded to the doses of phosphorus. Phosphorus was a modulator of dry biomass production of roots and of the production of nodules and the number of nodules of macrotyloma. The content of calcium present in the soil, together with the increase of the value of base saturation to 50%, was sufficient for the establishment and growth of the legume. Therefore, a supplemental dose of this nutrient was not required.

Floristic composition of weeds in a dystrophic Red-Yellow Argisol under the cultivation of cowpea, cv. BRS Novaera

Among the several factors that negatively influence cowpea culture, weeds have been responsible for the reduction of growth, development and productive performance of the crop, making it necessary to establish management strategies based on phytosociological studies of weed species in growing areas. Therefore, the objective of this research was to evaluate the floristic composition of weeds, aiming to identify the main species and their dynamics, and to consider their distribution in time and space as pertaining to the cultivation of a modern variety of cowpea, cv. BRS Novaera, in dystrophic Red-Yellow Argisol, in the Midnorth region of the state of Piauí, Brazil. The phytosociological survey of weeds was carried out in three sessions: the first one was immediately before the area was desiccated with glyphosate (15 days before sowing the cowpea), and the others were at 20 and 40 days after sowing (DAS). Following the quantification of species and number of individuals, the following phytosociological parameters were calculated: frequency and relative frequency; density and relative density; abundance and relative abundance; and importance value index. It was concluded that there were few changes in the floristic composition of the weed community according to the epoch of the phytosociological surveys. The main weed plants at 20 DAS of cowpea (vegetative phase) were Chamaesyce hirta, Digitaria insularis, Alternanthera tenella, Cleome affinis, Mollugo verticillata and Portulaca oleracea. At 40 days (reproductive phase), the weed species with a large establishment and acting as potential competitors with cv. BRS Novaera cowpea were Digitaria insularis, Chamaesyce hirta and Mollugo verticillata.

Growth and Development of Passion Fruit Seedlings under Irrigation with Salt Water and Biofertilizer

The yellow passion fruit is a plant climbing botanically that has a good geographical distribution in Brazil, with more than 150 species in the country. The presence of salts in soil and irrigation water is one of the main obstacles in agriculture in the world, caused by low rainfall and high evapotranspirative rates causing the salts to accumulate in the soil. However, alternatives have been sought to try to mitigate such limitations of seedling production, such as the use of biofertilizers in the soil. In this way, the objective was to evaluate the growth and development of yellow passion fruit seedlings under the effects of irrigation water salinity and the use of bovine biofertilizer on the substrate. An experiment was carried out in a greenhouse in the Center for Agrarian Sciences and Biodiversity, from october/2017 tomarch/2018, in county of Crato-Ceara, Brazil. The substrate used was the first 20 cm material of a yellow Red Argisol. The experimental design was completely randomized design (C.R.D) in a factorial scheme 5x2, referring to the electrical conductivity values ​​of the irrigation water: 0.5; 1.0; 2.0; 3.0 and 4.0 dS m-1, in the soil without and with common biofertilizer, with three replicates. The biofertilizer, after being diluted in non-saline water (0.5 dS m-1) in the ratio of 1:3, was applied only once to 10% of the substrate volume two days before sowing. The increase in the salinity of irrigation water negatively affected the initial behavior of the passion fruit seedlings in terms of growth and development, especially in the treatments that did not receive the organic feed.